Various types of mechanism have been proposed for devices for varying the valve property of the intake/exhaust valves of an internal combustion engine. For instance, JP2000-204917A and JP2011-185092A disclose valve rest mechanism that can selectively prevent the operation of some of the valves.
According to a previous proposed valve rest mechanism, a valve lifter interposed between a drive cam and a valve is internally provided with a switch pin that can selectively move between the first position and a second position under oil pressure. At the first position, a stem end of the valve abuts an abutting surface defined on the switch pin so that the valve lifter is enabled to drive the valve into the open position when the valve lifter is actuated by the cam. At the second position, the stem end of the valve is received in a through hole formed in the switch pin so that the valve is kept in the closed position because the valve stem advances into the through hole without being pushed by the valve lifter even when the valve lifter is actuated by the cam.
In this valve rest mechanism, a first valve spring and a second valve spring are used, while the first valve spring is attached to the valve stem, the second valve spring is engaged by the bottom end of the valve lifter. Therefore, the first valve spring can be installed by compressing the first spring via a valve retainer, and securing the valve retainer to the valve stem by using a valve cotter. However, when installing the second valve spring, the second valve spring is required to be compressed via the valve lifter when positioning the valve lifter between the cam and the valve stem. Therefore, the assembly work tends to be highly complex. Furthermore, the pressure created during the assembly work may be applied to sensitive hydraulic component parts such as a lash adjuster. Therefore, a suitable countermeasure will be required.